what pre amp for ATC SCM 40v2 spkrs + 250.5 Pass Labs pwr amp

Thanks for your input @three_easy_payments, 
which model @tomic601 ? and what kind of system are you running?

my systems are visible on the virtual system page. The reference is an ARC REF5se preamp that while it does not meet the balanced standard that Ralph cites, make decent sound. It drives a 6 m length of Audioquest WEL cable effortlessly into Vandersteen M7 HPA amplifiers. I have used an inexpensive mogami set of XLR wire also with excellent sonic and low noise results.

I have spent more than a few hours listening to the Ayre KX-R preamp and it is an incredible bit of SS engineering. I have owned an Ayre power amp in the past and currently own and use in a recording studio an Ayre A2D converter - anything Ayre touch sounds good and is hyper well engineered.

just my two cents.

Ralph of course makes great gear also!

BTW the REF 3 is an excellent preamp

So then I kindly ask which SS pre-amps are you aware that meet these ideals that you mentioned earlier?

I don't keep track of them but as I mentioned earlier its usually pretty easy to tell if the preamp supports the standard. If it has RCAs in addition to XLRs as main outputs, and does not have either an output transformer or switch to go between the two outputs, then it does not support the standard. You can also ask the manufacturer of course; sometimes they will know but IME sometimes they won't; I've found many that don't seem to know that the standard exists.

But to be clear, stuff can sound just fine if it doesn't meet the standard- the ARC Ref3 is a good example as are the Pass Labs preamps. But you will find that you have to be more careful about the interconnect (which might cost as much as the preamp itself) and you could also run into ground loop issues. The insidious thing about a ground loop is they can cause degradation of the sound without making themselves known by obvious symptoms like a buzz. These are the things that balanced operation is meant to solve!


So if the preamp isn't going to support the standard, IMO/IME you are just as well off exploring single-ended preamps too.


Its the lack of support of the balanced line standard in high end audio that is why there is controversy in high end about which sounds better. All I can say to that is if you hear balanced line done right, there's no going back! But to do it really right, you have to support the standard.

While Ayre has always made excellent sounding products IMO, their preamps don't appear to support the standard- every one that I've seen has a single-ended output beside the balanced output.

@atmasphere  

I've done some research and my findings are rather interesting. 

A) I was aware pro gear is all balanced- as they need to run long cables etc. As such my crown amp only has XLR inputs but they are also NOT AES 48 certified, there is no certification on the amp nor in the owner's manual, nor is it on newer crown amps as shown on their website. 

B) Secondly, I think I've only really seen (in 20years) 1 amp or pre-amp (I don't remember which) that only had XLR connections. 

C) PIN 1 in XLR is ground, if source is RCA then PIN 1 needs to be jumped with PIN 2 as PIN2 then becomes ground (and not balanced anymore). This case is true for my PASS amp 250.5.
Meaning that in differential configuration on my PASS amp PIN 2 and PIN 3 are not connected to ground because PIN 1 is ground.

I also don't understand why you would promote AES48 as a standard that allows for "superior" sound when "almost" no one uses this standard. Pro audio and Audiophile gear has been around for over 40years... 

You also mention IIRC Rowland made a balanced amp but didn't "support the standard" so this means that manufacturers don't need to support the standard in order to make a true balanced design? 

So this basically means there wasn't a problem in the first place, AES 48 is just a stamp of approval (that most manufacturers though following the design chooses not to apply for the certification). And as such brings me to the next point where you say

  "But you will find that you have to be more careful about the interconnect (which might cost as much as the preamp itself) and you could also run into ground loop issues."
Why would one need to spend $1000 on RCA interconnects to avoid a ground loop? when one could just use the XLR and it's shielded.

I'd like to get your input in all this confusion. 
Thanks